This application claims the priority of German Patent Document 199 54 978.8, filed Nov. 16, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a seat part for a vehicle seat of the type where a seat cushion which is covered by an air-permeable cushion cover, with at least one foam support and can be actively ventilated, and on a top surface of the seat part formed by stitched-down seams are a central and a front level seat surface and two border beads which bound the level seat surfaces laterally, said seat part having a heating mat arranged between the seat cushion and the cushion cover, said heating mat belonging to an electric seat heater.
In a known seat part of this type, shown in German Patent Document DE 196 28 698 C1, corresponding to U.S. Pat. No. 5,902,014, the seat cushion comprises a foam support accommodated by a cushion carrier, and a ventilation layer which covers the foam support over its entire surface area, capable of air flowing through it and made of a coarse-meshed knitted spacing fabric, and a pressure-distributing layer which rests on the ventilation layer and made of nonwoven fabric or open-cell foam. Introduced between the cushion cover and the pressure-distributing layer is a cover filling which is made of wool fleece or cut open-cell foam and accommodates the electrical heating conductors of the electric seat heater. For active ventilation of the seat cushion, the foam support has a multiplicity of air channels passing through it, said channels opening out, on the one hand, at the ventilation layer and, on the other hand, at the underside of the foam support, said underside being directed away from the ventilation layer. Inserted in each air channel is a miniature fan which takes in air beneath the seat cushion and blows it into the ventilation layer. The air spreads out in all directions in the knitted spacing fabric and, when the seat is not occupied, flows through the air-permeable cushion cover, which brings about rapid cooling of the cushion surface which has been heated, for example, by the sun. When the seat is occupied, the air flows along in the knitted spacing fabric of the ventilation layer and emerges again at the open ends of the seat cushion. It produces an air humidity gradient in this case and leads away the air humidified by the individual sitting on the seat. On account of the layer construction of the seat cushion, such a seat part has very good through-ventilation and long-term dimensional stability, but its high production costs mean that it is only used in vehicles in the upper price bracket.
In a likewise known vehicle seat described in U.S. Pat. No. 5,516,189, the heating conductors of the electric seat heater are embedded in a rubber or foam layer around which a cover made of flexible plastic or textile material is positioned. Such a completely preassembled heating mat facilitates the production of the seat cushion and seat.
An object of the invention, in the case of a seat part with seat heater for vehicle seats of the type mentioned above, is to ensure good through-ventilation and long-term dimensional stability.
This object is achieved by a perforated heating mat where the perforations are designed to be substantially sparser in an area of the central level seat surface than in areas of the front level seat surface and the border beads.
The seat part according to an embodiment of the invention has the advantage that optimum air guidance and good ventilation of the seat region are achieved by the perforation arrangement of the heating mat. According to a preferred embodiment of the invention, in order to reduce the production costs, a rubberized-hair layer serving for guiding and distributing air in the seat cushion covers the foam support directly, and the heating mat rests on the top side of the rubberized-hair layer. In addition, the reduction in the number of perforation holes per unit surface area in the region of the central level seat surface, which predominantly absorbs the seat pressure, achieves optimum sitting comfort and relatively long-lasting dimensional stability of the foam material of the foam support.
Advantageous embodiments of the seat part according to the invention along with expedient developments and configurations of the invention are constant diameter perforation holes and the foam support has a plurality of air channels pass through the foam support, said channels opening out at the rubberized-hair layer and at an underside of the foam support, said underside directed away from the rubberized-hair layer, and arranged in each of the air channels is a miniature fan which blows air towards the rubberized-hair layer.
According to an advantageous embodiment of the invention, the density of the perforation holes in the region of the central level seat surface is reduced to approximately half the density of the rest of the perforation holes. Such a reduction in the perforations in the central level seat surface has proven particularly expedient in providing a balance between through-ventilation and dimensional stability.
The invention is described in more detail hereinbelow with reference to an exemplary embodiment illustrated in the drawing by schematic illustrations.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.